Not Applicable
Not Applicable
Not Applicable
Air-conditioned spaces are typically equipped with a wall mounted thermostat that controls operation of a building""s cooling equipment. The wall thermostat is often fitted with a fan switch that allows the occupants to place operation of the air conditioning equipment into xe2x80x98coolxe2x80x99, for automatic control of the cooling equipment, or to switch the equipment to xe2x80x98off.xe2x80x99 Many thermostats also incorporate means for automatically controlling heating equipment. If the thermostat is used for the control of both heating equipment and air conditioning equipment, it may typically be fitted with a switch that permits the occupants to select the xe2x80x98heatxe2x80x99, xe2x80x98coolxe2x80x99 or xe2x80x98offxe2x80x99 modes. Operation of the circulating fan is often controlled by means of a separate switch that allows for xe2x80x98autoxe2x80x99 or xe2x80x98onxe2x80x99 operation of the circulating fan. When the fan switch is in the auto position, the circulating fan is operated whenever the air conditioner is operating. In this manner conditioned air is circulated throughout the inner spaces of the controlled area. If the fan switch is indexed to the xe2x80x98onxe2x80x99 position the circulating fan is operated continually. A large percentage of thermostats are also fitted with a clock that facilitates automatic set-back of the of the thermostat""s setpoint.
The function of the thermostat is to maintain the temperature in the controlled space within comfortable temperature limits. Upon a rise in the sensed temperature to the setpoint of the thermostat, the thermostat automatically begins operation of the air conditioning system. In consequence to operation of the cooling equipment, the temperature within the controlled space is maintained within comfortable levels. After the thermostat detects a substantial decrease in temperature, it stops operation of the air conditioning equipment. The cycle is repeated again as the sensed temperature rises and falls. Under average daytime hours, the occupants of the building in which the thermostat is located find little need to intervene with the automatic operation of the air conditioning equipment. However, the described mode of operation fails to provide uniform comfort under a variety of outdoor conditions and at all hours of the day. The deterioration in comfort levels is particularly noticeable to occupants after they retire for the evening. This rise in human discomfort in the occupied spaces is due to a number of causes.
Whenever a building is under a relatively high heat load, the building""s air conditioning system is cycled on and off frequently as the wall thermostat responds to detected rises in the air temperature. The resulting frequent operation of the air conditioning system helps to maintain not only the temperatures within the building but the humidity as well. Frequent operation of the building""s air conditioning system, together with the attendant operation of the circulating fan, ensures that conditioned air is circulated in a timely manner to all areas of the building. As a result, comfort levels are generally well maintained during the daylight hours of hot days. However, the sensible heat load on a building will generally fall after dusk. Consequently, both the frequency and the duration of operation of the air conditioning system, and the circulating fan, will decrease after dusk. Regardless of the cooling load on the building, the temperature near the thermostat will be adequately maintained. However, the less frequent operation of the air conditioning equipment may cause temperatures in areas remote from the thermostat to rise to uncomfortable levels. These temperature rises occur primarily during the longer xe2x80x98offxe2x80x99 cycles of the cooling equipment. After nightfall, the humidity in occupied bedrooms will also rise due to human respiration. The combination of both a rising temperature and a rising humidity especially contribute to the discomfort of occupants.
The thermostat typically provided with an air conditioning system to detect the controlled temperature is generally located on a wall that is central to the area where the building""s occupants spend most of their time during the daylight hours. In a residence, the location chosen for the thermostat is generally not on a bedroom wall. In two-story homes, the wall thermostat would most often be located on the first floor of the residence. Most, if not all, of the bedrooms in a two-story home would generally be on the second floor of the residence. Due to the solar radiation that strikes the building during the daylight hours, the upper and outer portions of the building become heated and rise in temperature. These heated portions of the building act as what may be best described as a xe2x80x98heat sink.xe2x80x99 After the sun sets, these heated portions of the building continue to provide a source of heat that is gradually transferred to the air in the inner spaces of the building. The upper areas of the building continue to receive a disproportionate amount of heat that is transferred from the ceilings, walls and attic areas of the house. As a result of this delayed heat transfer, the air temperatures in the upper spaces of a two-story building may rise considerably above the first floor temperature after dusk.
If the circulating fan is not operated periodically, the humidity in the bedrooms will rise as a result of the respiration of the occupants. The increased humidity will cause a xe2x80x98stalexe2x80x99 effect in a bedroom due to the relatively small volume of air contained within a bedroom. The problem is momentarily remedied if the air conditioning system operates and removes moisture from the air. Alternatively, periodic operation of only the circulating fan can ameliorate the problem. If the fan is operated for an appropriate period of time, the stale air from the bedrooms will be diluted with less humid air from other areas of the building. Periodic operation of the fan will also mix the hotter air from the upper levels of a building with air from the lower story thereby often causing the thermostat to call for operation of the cooling equipment. This operation, in turn, both lowers the temperature throughout the building and simultaneously dehumidifies the circulated air. As a result, the humidity levels are improved along with the improved temperature levels.
Continuous operation of the circulating fan would alleviate the cited problems that are encountered due to long inactivity of the circulating fan. In fact, this practice is often used. However, continuous operation is undesirable for several reasons. First, the sound of the fan continuously operating is considered by many to be disconcerting. Furthermore, continuous operation is wasteful of electrical energy.
Timers have been used in a variety of methods to provide periodic operation of the circulation fan. Some of these methods offer a measure of improved comfort. Nevertheless, all of the known methods contain considerable disadvantages. Some methods provide operation of the circulating fan both at times when that operation would be helpful but also at times when the operation would be bothersome and wasteful of energy. Other arrangements require the frequent, and inconvenient, intervention of the building""s occupants to initiate and terminate timer operation.
This invention generally pertains to the field of indoor environmental control and, more specifically, to a means of automatically operating the indoor circulating fan of an air conditioning system. The operation of the circulating fan is under the direction of a controller that records the pattern of usage of the building""s air conditioning system, conducts calculations to determine when operation of the circulating fan would improve the comfort of the building""s occupants, and, based on those calculations, intermittently operates the circulating fan throughout a period of time.
The present invention consists of a control that incorporates a computing device to predict when operation of the building""s circulating fan would improve comfort levels within the controlled spaces. The prediction is made in accordance with programmed algorithms that essentially synthesize the pattern of usage of the air conditioning equipment. Based on the results of the calculations, the control, which is herein termed the xe2x80x98predictive controlxe2x80x99, then acts to periodically operate the fan throughout a period of time. Operation of the fan is completely automatic, and, since operation is conducted only when required, the control affords an economic means of improving comfort levels within the building. After the initial installation, no human intervention is required to ensure proper operation of the device. The invention provides for improved comfort levels primarily during evening hours and particularly in buildings of two or more stories where people sleep.
In one possible embodiment of the invention, the predictive control would be incorporated into a separate enclosure that is located remote from the thermostat that controls operation of the building""s air conditioning system. A configuration of this type may be used, for example, to conveniently and economically retrofit existing installations. On the other hand, the function of the logic device used in the predictive control could be performed by a microprocessor or similar small device. Accordingly, the device could be very small and could readily be incorporated within the enclosure of a wall thermostat. If incorporated into the wall thermostat, the invention could be used in both new installations as well as retrofit installations. It is expected that the most common usage of the invention will be in this later mentioned configuration.
To effectively predict when fan operation would be desirable, the predictive control conducts an analysis of the pattern of air conditioning operation. To perform that function, the predictive control first records air conditioning operation over time. The program then examines the recorded information to determine if fan operation is warranted and, if so, when that operation should be initiated. A number of criteria are applied to make the determination. If fan operation is to be initiated, the frequency of fan operation, the duration of the fan operation and other pertinent parameters are selected to suit the anticipated need. The calculation is conducted only in consequence to detected air conditioning operation. As a result, there will be some days when operation of the fan is frequent and of a relatively long duration. Other days, the fan would be operated less. On many days the fan will not operate whatsoever. If the calculations indicated fan operation is warranted, then fan operation is subsequently initiated. In a simplified version of the invention, the predictive control would merely determine if fan operation is required. If the determination is affirmative, then fan operation would be scheduled to occur over a period of time.
In a preferred embodiment of the invention, the control estimates when the adult occupants will retire to the bedrooms for the evening. That estimation is based on a determination of the significant decrease in operation of the air conditioning equipment that normally occurs at sunset. If fan operation is to be initiated, the beginning of that fan operation is scheduled to correspond to a time when the temperature and humidity in the upper rooms of a two-story building would begin to rise, namely several hours after dusk. More exactly, it is expected that this occurrence would generally coincide with the time when the building""s adults retire for the evening.
In an alternate embodiment of the invention, a clock is used to estimate the normal time when the occupants retire. The pattern of usage of the air conditioner is then examined with the programmed criteria to determine if fan operation is warranted. If fan operation is warranted, the fan is subsequently operated by the predictive control for a suitable number of cycles and starting at a selected time.